Method and apparatus for pressure counterbalance in fluid machines



May 26, 1964' H. M. HUFFMAN EI'AL 3, 3

METHOD AND APPARATUS FOR PRESSURE COUNTERBALANCE IN FLUID mcnmss 3 Sheets-Sheet 1 Filed Oct. 21, 1963 FIG] FIGS

' INVENTORS HERMAN M. HUFFMAN y CHARLES K. MUTH ATTORNEYS y 26, 1964 H. M. HUFFMAN EI'AL 3,134,336

METHOD AND umanus FOR PRESSURE COUNTERBALANCE IN mun MACHINES led Oct. 21, 1963 3 Sheets-Sheet 2 mm M; gm

39 'INVENTORS HERMAN u. HUFFMAN v CHARLES K. MUTH 'ym L'W ATTORNEYS May 26, 1964 H. M. HUFFMAN ETAL 3, 6

METHOD AND APPARATUS FOR PRESSURE COUNTERBALANCE IN FLUID MACHINES Filed Oct. 21, 1963 3 Sheets-Sheet-S FIG. II. 2m

HERMAN M. HUFFMAN CHARLES K. MUTH ATTORNEY gnembers.

3,134,336 METHOD AND APPARATUS FOR PRESSURE COUNTERBALANCE IN FLUID MACHINES- Hernian Martin Huffman, 2142 Roseland, and Charles Komus Muth, 3813 Oakland Drive, both of Kalamazoo, Mich.

Filed Oct. 21, 1963, Ser. No. 317,837

'11 Claims. (Cl. 103-126) The present invention relates to pumps of the turbine, centrifugal gear and piston varieties, whether of the fixed or variable pressure type and more particularly to means for counterbalancing dynamic stress applied to the bearing areas thereof emanating from the reactance force on the pump rotor or elements at the outlet, and is a continuation-in-part application of our copending application Serial Number 142,824, filed October 4, 1961. In a more general sense, the present invention involves a method and apparatus applicable to all fluid machines for counteracting thrust imbalance by reason of pressure differential between inlet and outlet conditions. Still more particularly, the present invention is directed to providing an hydraulic counterbalancing force in such a way as to avoid pressure loss arising from so called pressure or film breakthroug asll'occurs under shock load conditions as between high pressure and low pressure areas in and adjacent to the zone where the hydraulic counterbalance is applied.

At least as earlyas the United States Letters Patent 1,379,587 to I. P. Fisher, in. 1921,. high pressure pump technology has recognized that the high pressure side of the pump exerts detrimental reactance force on the rotors tending to cause serious axial and radial displacement of pumping elements with accompanying loss of pump efficiency and serious damage to journals, case, and pumping members. In avoidance of axial displacement it was proposed that the high pressure from the outlet side of the pump be utilized to exert a counterbalancing axial force on the shaft thereby maintaining satisfactory mesh, say, as between pump rotors or gears and the like. This ultimately involved axially movable pressure loaded bushings wherein the delivery pressure at the pump outlet was utilized to balance the thrust on the pumping members. In 1921 Fisher merely proposed circulating the high pressure fluid through the bearings to the low pressure side. It hence is generally conceded that utility resides in em- United States Patent Office ploying the high pressure as a ballast against forces .gen-

erated by the pump and reacting against the pumping Some, like Roth et al. in United States Letters Patent 2,420,622, have proposed axial application of counterthrust while others have dealt with radial counterbalance. All attempts have sought to apply a load I approximating the eccentric loading at the pumping members as transmitted to the shaft thrust plates and other bearing areas. Quite reasonably the efficiency of such counterbalancing developments have depended more or less upon the application of the counterbalancing force and the problem of loss of counterbalancing pressures as a consequence of loss of seal. Hence, much of the art has been devoted to accomplishing an effective seal subject to the difiicult conditions imposed by a moving shaft in relation to a bearing surface and wherein the shaft is further subject to occasional shock loading as under variable pressure conditions which tend to upset the counterbalancing factor and ruin the efliciency of sealing in conventional channels, grooves, and the like. Once a breakthrough occurs, restoration of the counterbalance is difficult initime to prevent serious pump damage.

This invention proposes as its principal object an improved counterbalance method and means exactly applicable and locatable so as to equate against the'eccentric forces developed in high pressure fluid machines. As

'shaft in selected area relationship in the region of the shaft bearing. Hence another of our objects is to pro- 'vide a selectively located thrust applying pressure pad structure to a bearing in counteraction to eccentric forces developed at the pumping member on the shaft. As will 'be further appreciated the invention comprises a unique safeguard against loss of compensating or counterbalanc-- ing pressure thereby providing excellent assurance against destruction of counterbalance under shock conditions.

This, as will be seen, is accomplished by providing a plurality of separate .concentricchannels,- defined by adjacent lands, each alternate or other selectively spaced channels, being independently subjected to high, pressure substantially static loading, saidgrooves trapping fluid under high pressure and creating a film of fluid between adjacent lands and said bearing surface. In this way using closed grooves, film breakthrough as to one of said passages does not impair the thrust imparted to the shaft or other bearing surfaces by the other of the separate channels. The hydraulic fluid provides a pressurized film barrier between lands and shaft or moving surface. As will be appreciated this application may also be applied to linear or angular sliding bearing. Utilizing concentric channels the concept is equally applicable to thrust plates bearing or shouldering on the pump rotors. It will be likewise appreciated that this invention includes a new and useful method for counteracting back thrust in fluid machines wherein there is a differential in pressure as between inlet and outlet thereof. Concentric, as used herein with reference to the plural lands and grooves, is also intended to include plural closed channels and adjacentclosed separating lands of varying intervals as well as equal intervals between adjacent channels and lands.

Other objects will be increasingly obvious to those skilled in the art' as the description proceeds.

In the drawings:

; FIGURE 1 is a side elevation view of a gear pum and including within its housing structure the embodirn iit of the present invention.

FIGURE 2 is an end elevation ture shown in FIGURE 1.

FIGURE 3 is a transverse plan view section through the pump as shown in FIGURES 1 and 2 and taken on the line III-III of FIGURE 2 and revealing the control passages of the present invention.

FIGURE 4 is a transverse elevation view section through the pump of FIGURES 1 and 2 and taken on the line IV-IV of FIGURE 2 and indicating high pressure leads to the shaft bearing areas.

FIGURE 5 is an elevation view through a sleeve bearing in accord with the present invention and indicating the alternating concentric lands and grooves provided in the working base of the bearing.

FIGURE 6 is a section view taken on the line VIVI of FIGURE 5.

FIGURE 7 is a somewhat schematic perspective view of the counterbalance structure and illustrating the structure of the present invention in a fiat use setting.

FIGURE 8' is a full section cut-away view showing a single bearing in accord with the present invention fitted into a pump housing and the bearing accomplishing selective bias pressure on the shaft journalled therein by use of high pressure fluid, and indicating the migratory path of high pressure to low pressure area surrounding the outer portion of the pump case.

FIGURE 9 is a perspective view of a counterbalance structure in a flat use setting in accordance with this view of the pump struc- Patented May 26, 1964 General Description In general a pump in developing a selected operating pressure, absorbs a reacting thrust 'from the pumped fluid material. This thrust is backed up against the pump members or rotors. In gear pumps the reacting force is applied to the rotors or gears on the outlet side thereof and the bias to the rotors causes pump imbalance. The imbalance from the reactance thrust is translated to shaft, thrust plates and bearings to cause localized wear areas which eventually render the pump ineffective and allow the rotors, impellers, pistons or gears to misalign themselves with substantial attendant drop in eiiiciency and serious damage to the moving members within the pump or casing, bearings, and seals within the pump. These detrimental characteristics are well known and reach significant troublesome proportions in high pressure pumping applications. In general, the surface area of the moving parts in exposure to high pressure conditions at a pump outlet and the magnitude of the pressure viewed as a differential between negative pressure at the inlet side of the pump and positive pressure at the outlet side provide an hydraulic approximation of the imbalance. The resolution of these forces from rotors, to shafts, to bearing surfaces determine the points where the imbalance is serious. These positions vary from one pump to another. Rotor or pumping member size and design are hence factors in determining whether the resultant force from the high pressure reaction will be applied in a radical, eccentric or thrust sense. A very good appreciation of these factors is understood by reference to United States Letters Patent 2,212,994, issued to Vrolix in 1940. A recognition of the problem has resulted in many solutions wherein high pressure fluid is bled from the outlet side of the pumpand selectively applied to various areas of the pump in order to compensate or balance the imbalance in the pump. Theoretically this approach is sound. However, providing means for effective application of balancing forces has'been primarily directed to channelling conducting lines through the pump with return to the low pressure entry side of the pump and incidentally applying pressure to specific areas in the pumping structure. Such systems do not contemplate a solution to the problem of shock loading of high pressure pumping systems which result in momentary surges seriously upsetting the delicate pressure redistribution systems, selectively applied to specific counterbalance points keeping in mind that they may vary from one pump to another. The present invention thus encompasses the use of a high pressure line bled from the pump outlet and employes unique pressure pad means to accomplish avoidance of pressure film breakthrough of fiuid as arises under surge or shock loading and to apply the pressure in a localized manner to selective points in the pump. Thus the invention comprises a unique combination of spaced-apart and alternating closed lands and closed grooves in generally concentric relation so that the lands are in plane register with a bearing surface and the grooves provide pressure applying areas imparting counterbalancing thrust to specific bearing areas, as for example in moving surfaces such as shafting, thrust plates as they abut rotors and the like. As will be appreciated the lands are separated from the shaft surface by the pressurized oil film. Further, the unique pressure pads are provided with a high pressure mainfold in communication with a lead from the high pressure outlet side of the pump thereby developing a pressure equality in the pressure pads with the delivery pressure conditions. The conception may be viewed as a substantially hydrostatic application of pressure but whereinthe plural grooves in concentric form substantially avoid pressure drop and fluid breakthrough over the entire counterbalancing surface. The result obtained by the present device is a substantial avoidance of pump imbalance even under shock loading of the pump. The method and apparatus has application in a wide variety of fluid machines, both pumps and motors wherein a substantial differential between inlet and outlet pressure conditions exists. In some instances true concentricity as between adjacent lands and grooves is not maintained as where a pressure gradient is sought to be met by localized special configuration of plural lands and grooves.

Specific Description Referring to the drawings; and specifically with reference to FIGURE 1, a pump 11 is shown of the gear pump type and comprising pump case members 12 and 13 sandwiching therebetween the rotor housing 14. A drive shaft 15 extends from the case member 12. Transverse of the shaft 15, an outlet 16 is defined by the rotor housing 14. By reference to FIGURE 2 it will be seen that an oppositely disposed inlet 17 is also provided as defined by the housing 14. As will be appreciated, the existence of an inlet and outlet is intended to generically describe a pump and the gear pump 11 is a convenient simply-understood pumping device. Material to be pumped enters the pump 11 through the inlet 17 and exits from the pump through the outlet 16. Hence vacuum or lower pressure conditions exist at the inlet 17 with respect to fluid served by the pump 11 and high pressure conditions exist at the out- By reference to FIGURES 3 and 4, the pump 11 will be seen to comprise a pump cavity 18 defined by the rotor housing 14 and the parallel spaced-apart thrust plates 19 and 20. The thrust plates 19 and 20 bear or shoulder against the rotor members 21 and 22. In FIGURE 3 only the rotor member 21 is shown, but as will be appreciated by reference to FIGURE 4, the action of these members are coordinated by meshing as is well known in the gear pump art. The rotor 21 is the driven rotor and the rotor 22 is the drive rotor. As appreciated, the drive rotor 22 is secured to the shaft 15 for rotation therewith, and the driven rotor 21 is secured to the shaft 23 for rotation therewithor thereon. A motor, not shown, is driveably connected to the pump drive shaft 15. The shafts 15 and 23 are journalled in bearings 24 and 25 and 26 and 27 respectively. The bearings 24, 25, 26, and 27 are supported in the pump case members 12 and 13. The thrust plates 19 and 20 are ported adjacent the inlet 17 and outlet 18, the ports 28 and 29 and 30 and 31, respectively defined therethrough, are in register with passages 32 and 33 and 34 and 35 provided in and through case members 12 and 13. Hence, passages 32 and 33 are in communication with high pressure fluid at the outlet 16 of the pump 11 and passages 34 and 35 are in communication with the low pressure inlet conditions prevailing at the inlet 17. This, as will be seen, provides a by-pass return communicating high pressure fluid back to the inlet side of the pump 11 and through the journal areas of the pump 11. The high pressure passages 32 and 33 lead to the bearing areas occupied by the bearing members 26 and 27 supporting the shaft 23 and the bearing areas occupied by the bearing members 24 and 25 supporting the shaft 15. The low pressure passages 34 and 35 are in communication with the outboard sides of the bearings 24, 25, 26 and 27. Seals 36 are provided about the high pressure ports 28 and 29 preventing loss of high pressure as between case members 12 and 13 and thrust plate members 19 and 20.

As thus described means have been provided to supply high pressure fiuid to the bearing area and to return leakage through the bearing area to the low pressure inlet side of the pump as led from the outboard ends of the bearing housing portions of the case members. Thus, the bearing area becomes a membrane through which fluid may flow by reason of the differential between high and low pressure areas. The advantageous use of this fluid flow membrane relationship requires further elaboration. Pressure is applied by means of cavities in the faces of the bearings 24, 25, 26 and 27 to the shafts 15 and 23. By reason of communicating the high pressure fluid to the cavities 36 in each of the inner faces of bearings 24, 25, 26 and 27 so as to apply counterbalancing pressure to thrust from the rotors 21 and 22 on the shafts 15 and 23. The small slippage of fluid by the bearings generally assists in lubrication and the movement of fluid is from high pressure to low pressure passages. In fact the shaft or moving part is separated from the bearing surface in normal operation by the pressurized fluid film.

Reference is now made to the detail FIGURE 5 wherein a sleeve bearing 37, embodying the present invention is shown in relationship to a pump rotor attached shaft 38. In detail, the bearing 37 is seen in FIGURES 3 and 4 as bearings 24, 25, 26 and 27. For clarity the bearing 37 is shown resting in a bearing shoulder of a casing 39. A channel 40 is provided on the outer face of the bearing 37. The channel 40 is located in substantial register with a high pressure passage 41 such as described in reference to FIGURES 3 and 4. Orifices 42, transverse of the axis of the channel 41 are provided through the bearing 37. As shown, the orifices 42 are radially disposed. However, in flat bearing applications (FIGURES 7, 9 and 11), the orifices need only communicate through the bearing. As shown in FIGURE 7 the orifices 42 are in flow communication wtih grooves 43 spaced apart by lands 44, the lands 44 being in bearing contact but for the fluid film with the shaft 38. This is better illustrated by reference to FIGURE 6. Each of the grooves 43 closes upon itself and through the corresponding orifices 42 is supplied with high pressure fluid. The grooves 43 are concentrically arranged as shown and increase in area progressively as ring grooves move from the inner rings to the outer rings, each being spaced from the next by the adjacent concentric lands 44. This increasing area relationship also holds true for the lands 44.

In some instances the. alternating closed channels or grooves 43 and closed lands 44 are contoured so that the intervals or spacing between adjacent grooves or lands is varaible or eccentric instead of being truly concentric in form. It is not necessary that each groove 43 be supplied with high pressure fluid by way of a port or passage 42. In certain instances it may be desirable to port only alternate or randomly spaced grooves depending upon the particular application involved. In such an event the intervening non ported grooves act as traps receiving and storing any fluid leakage from adjacent grooves. High pressure films are established between the adjacent lands to create and exert a counterbalancing pressure.

In FIGURE 7, a flat bearing 45 is shown in which the land and groove pattern, radially provided to a shaft'in FIGURE 5, is clearly expressed. The lands 46 and grooves 47 are arranged in alternating concentric manner to provide for pocketing of high pressure fluid supplied to the grooves 47 through the orifices 48. Lubricating channels 49 may or may not be supplied depending on the specific application intended. They are always utilized to dump to low pressure and separate the outermost land from the balance of the bearing surface. FIGURES 9 and 11 illustrate similar flat use settings wherein orifices 48' and 48" are communicative with alternate and every fourth channel or groove 47' and 47" respectively. Of course, the orifices 48 may be randomly spaced at other intervals as desired.

In FIGURE 8 the pressure pad bearing structure in accord with FIGURES 6 and 7 is shown in cutaway detail form, indicating high pressure application and migrating flow to the low pressure area. Similarly FIGURE illustrates a pressure pad bearing structure in accord with FIGURE 9.

The arrangement of lands and grooves, in either the FIGURE 5 or FIGURE 7, 9 or 11 structures are localized or occupy only a restricted portion of the bearing member surface so that in installation the pattern of lands and grooves is selectively applicable to a desired area sought to be subjected to counterbalance. However, the outer land is preferably adjacent a pressure relief groove as shown. In general as by reference to FIGURES 3 and 4, the pressure pad bearing structures are in opposed position to the outlet of the pump. The pressure pad bearing structures are inserted in the case elements so as to locate the thrust application in the most advantageous spot. Likewise it will be appreciated that the area relationship determined by the groove size spacing and number is variable in accord with variance in application. While the concentric lands and grooves have been shown as rectangular in plan pattern, it will be likewise appreciated that oval, irregular and round concentric or eccentric arrangements are embodied in the spirit of the invention and, as shown, circumferential and plane usages are contemplated. In the preparation of the hydrostatic or-pressure pad bearings, as herein described, powder metallurgy techniques as well as mechanical channeling as by milling or grinding and chemical channeling as by etching have proved successful.

' The method, set forth therein, for balancing dynamic and shock loads as reacting against fluid machine components will be appreciated to comprise the leading of a high pressure fluid from the high pressure side of the fluid machine to a localized channeled area portion of selected bearings and wherein the channels are concentric and separate. Then the fluid is passed through the concentric channel at high pressure, each of the lands between hte channels accomplishing a film of fluid between bearing and shaft or moving part and each of the channels and grooves in accord with its area applying a thrust in a counterbalance manner to anticipated imbalance. Then the method includes conduction of the exhausted fluid from the bearing area to the low pressure side of the fluid machine. This process is both versatile in providing selected areas of pressure conditions and eliminates troublesome film breakthroughs which diminish or fully deplete the counterthrust provisions.

In operation, the high pressure fluid as applied to the bearings which include the concentric ring hydrostatic pad create a pressure pattern counteracting the dynamic forces resulting from the pumping operation. In the event of shock loading applied to the bearing area through, for example, reacting thrust on the rotors, then the concentric grooves can permit a local film breakthrough as between low and high pressure areas without seriously impairing the performance of the unaffected other concentric fluid applying grooves. Restoration of static conditions after breakthrough is relatively rapid and a more stable pumping structure results. Pressurized lubrication utilizing the pumped fluid is ideal and sudden changes in pressure do not result in use interruption or pump damage. The lands are kept fully supplied from the high pressure film creating source and the structure is not effected by pressure drop observed in prior devices. The pump balance is more nearly maintained as uniform and the form of the described pressure pad bearings admit of selective application of counterbalance pressures with selected patterning of thrust application. In instances where alternate or randomly spaced grooves communicate with a high pressure fluid source, the intervening grooves trap any fluid leakage and maintain the desired fluid film between adiacent lands and theshaft. In the event of severe shock waves. where local film breakthrough occurs and fluid is forced from a ported groove back through the orifice communicating therewith, the trapped fluid in the intervening non ported grooves will maintain a pressurized fluid film between the opposing bearing surfaces throughout a portion of the pressure pad thereby tending to eliminate wear even under cases forces.

As will be appreciated the description has related to pressure pads as applied to both flat and cylindrical bearing surfaces, but the concentric land and groove form of pressure applying pad in pumps and like structures will be understood to have usage in thrust plates, and other bearing contact areas whether the counterbalance is applied in a thrust or radial load use setting.

While the description has related primarily to pumps it will be appreciated that it also relates to other fluid machines as for example for a fluid motor wherein a differential of pressure exists as between inlet and outlet and wherein it is desirable to counteract imbalance arising from high pressure thrust on the rotors, pistons, and the like.

Having thus described operative embodiments of our invention it will be appreciated that improvements and modifications will be suggested to those skilled in the art, and such improvements and modifications falling within the spirit of the invention are intended to be included herein limited only by the scope of the hereinafter appended claims.

We claim:

1. In a fluid machine having a differential between outlet and inlet pressures. a device for applying a counterbalance to unbalancing thrust comprising: a pressure pad area in a bearing surface including a plurality of alternating lands and grooves each closing on itself; means for communicating high pressure fluid to each of said grooves; and a low pressure chamber adjacent and communicating with at least a portion of said outer groove forming a pressurized film of fiuid between adjacent lands in said bearing surface resisting leakage of fluid between said adjacent grooves.

2. In a fluid machine having a differential between inlet and outlet pressures, a device for providing a counterbalance to unbalancing thrust comprising: a pressure pad having a bearing surface and including concentric grooves therein; means for communicating high pressure fluid to each of said grooves; and a low pressure chamber adjacent and communicating with at least a portion of said outer groove forming a pressurized film of fluid between adjacent lands in said bearing surface resisting leakage of fluid between said adjacent grooves.

3. A pressure pad counterbalancing bearing for pumps having a low pressure inlet and a high pressure outlet and wherein high pressure outlet fluid is utilized to counterbalance outlet pressures acting against pumping elements comprising: a bearing having a substantial thickness and provided with a bearing contact surface and wherein the bearing contact surface is provided with spaced-apart separate concentric grooves forming spaced continuous lands in said bearing contact surface; orifices through which fluid may pass in each of said-grooves and transverse in axis to said bearing surface; a high pressure channel forming a fluid manifold in said bearing and in fluid communication through said orifices to said grooves; and a low pressure fluid discharge channel in said bearing surface adjacent -;at least a portion of said outer groove, said discharge channel communicating with said low pressure inlet whereby a pressurized film of fluid is formed between said lands in said bearing surface and said pump element resisting leakage of fluid between said adjacent grooves in said bearing contact surface, substantially all fluid leakage from said bearing pad occurring between said outer groove in said bearing contact surface and said low pressure discharge channel.

4. A pump bearing for counterbalancing thrust on a pump element supported in said bearing comprising: a bearing having a bearing surface; a plurality of alternating concentric lands and grooves in said bearing surface, said lands being co-planar with said bearing surface, and said grooves extending below said bearing surface; a manifold channel communicating with the high presof extremely severe shock sure outlet of said pump defined in the back of said bearing; separate passages connecting each of said grooves with said channel; and a low pressure channel adjacent said outer groove whereby a pressurized film of fluid is formed between said lands and said element supported in said bearing, said pressurized film of fluid resisting leakage of fluid between said adjacent grooves.

5. A counterbalance structure for pumps comprising: a pump having a low pressure inlet and a high pressure discharge outlet; a pump body; a substantially static fluid pressure line defined through said pump body and in communication with the high pressure discharge outlet of said pump; a shaft in said pump; a bearing about said shaft; a plural passage thrust imparting element in selected pressurized fluid bearing contact in said bearing and against said shaft, said passages defined by said thrust imparting element connected to said static line; a plurality of closed spaced grooves one within the other in said bearing surface bearing against said shaft, said grooves communicating with said passages and forming a plurality of spaced lands in said bearing surface; and a low pressure return line defined through said pump body in communication with the exterior of said bearing and connected to the suction side of said pump, whereby a pressurized film or fluid is formed between said bearing and said shaft within said bearing, said pressurized film of fluid resisting leakage of said fluid between said adjacent grooves and said bearing surface.

6. A method for balancing dynamic loads in pumps against surge or shock conditions comprising the steps of: leading high pressure fluid from the outlet of a pump; forcing said fluid through a bearing area; pocketing said fluid in selected concentric'separate channeling so as to provide a pressure area, said pressure area having a substantially uniform pressure gradient throughout acting against the pressure imbalance in said pump, thereby preventing a film breakthrough from damaging said pump and the bearing surfaces thereof; and providing a 'low pressure return area leading said fluid to return stream at the inlet of said pump.

7. In a fluid machine having a differential between outlet and inlet pressures, a device for applying a counterbalance to unbalancing thrust comprising: a pressure pad area in a bearing surface including a plurality of alternating lands and grooves each closing on itself; means for passing high pressure fluid to at least two of said grooves; and a low pressure chamber adjacent and communicating with at least a portion of said outer groove forming a pressurized film of fluid between adjacent lands in said bearing surface resisting leakage of fluid between said adjacent grooves.

8. A pressure pad counterbalancing bearing for pumps having a low pressure inlet and a high pressure outlet and wherein high pressure outlet fluid is utilized to counterbalance outlet pressures acting against pumping elements comprising: a bearing having a substantial thickness and provided with a bearing contact surface and wherein the bearing contact surface is provided with spaced-apart separate concentric grooves forming spaced continuous lands in said bearing contact surface; orifices through which fluid may pass into at least two of said grooves and transverse in axis to said bearing surface; a high pressure channel forming a fluid manifold in said bearing and in fluid communication through said orifices to said grooves; and a low pressure fluid discharge channel in said bearing surface adjacent at least a portion of said outer groove, said discharge channel communicating with said low pressure inlet whereby a pressurized film of fluid is formed between said lands in said bearing surface and said pump element resisting leakage of fluid between said adjacent grooves in said bearing contact surface, substantially all fluid leakage from said bearing pad occurring between said outer groove in said bearing contact surface and said low pressure discharge channel.

9. A pump bearing for counterbalancing thrust on a pump element supported in said bearing comprising: a bearing having a bearing surface; a plurality of alternating concentric lands and grooves in said bearing surface, said lands being co-planar with said bearing surface, and said grooves extending below said bearing surface; a manifold channel communicating with the high pressure outlet of said pump defined in the back of said bearing; separate passages connecting at least two of said grooves with said channel; and a low pressure channel adjacent said outer groove whereby a pressurized film of fluid is formed between said lands and said element supported in said bearing, said pressurized film of fluid resisting leakage of fluid between said adjacent grooves.

10. A device as defined in claim 9 including means passing high pressure fluid into alternate grooves.

11. A device as defined in claim 9 including means for passing high pressure fluid into randomly selected grooves as determined by the counterbalancing thrust to be applied.

for

References Cited in the file of this patent UNITED STATES PATENTS Johnson Feb. 5, Wood Ian. 5, Palmer Feb. 26, Vernon Jan. 2, Fisher May 24, Aker June 4, Vrolix Aug. 27, Roth et al May 13, Hoffer Sept. 14, Martellotti Dec. 18, Gerard Nov. 24, Dolza et al May 22, Conlon Mar. 17, Murray et al. June 23, Gaubatz Oct. 11, Booth et al. May 30, Conlon July 17, Conlon July 17, 

1. IN A FLUID MACHINE HAVING A DIFFERENTIAL BETWEEN OUTLET AND INLET PRESSURES, A DEVICE FOR APPLYING A COUNTERBALANCE TO UNBALANCING THRUST COMPRISING: A PRESSURE PAD AREA IN A BEARING SURFACE INCLUDING A PLURALITY OF ALTERNATING LANDS AND GROOVES EACH CLOSING ON ITSELF; MEANS FOR COMMUNICATING HIGH PRESSURE FLUID TO EACH OF SAID GROOVES; AND A LOW PRESSURE CHAMBER ADJACENT AND COMMUNICATING WITH AT LEAST A PORTION OF SAID OUTER GROOVE FORMING A PRESSURIZED FILM OF FLUID BETWEEN ADJACENT LANDS IN SAID BEARING SURFACE RESISTING LEAKAGE OF FLUID BETWEEN SAID ADJACENT GROOVES. 